Extending the encouraging confinement results in Tokarnak devices and further establishing scaling laws makes it essential to attain ion temperatures corresponding to the collisionless regime, where reactors will operate. Ohmic heating used in the present devices is self-limiting since the plasma resistance drops as the temperature increases. Neutral-beam injection heating is not only a supplemental heating scheme that is efficient and not self-limiting but is also a developed technology ready for application. Injection heaters have been developed at ORNL for ORMAK which are capable of supplying 60 kW to the plasma per injector with up to four units usable. These systems use 4 A of H+ and ions at 35-40 keV from a duoPIGatron ion source. These heaters are capable of increasing the ion temperatures in the 8 × 105 cm3 ORMAK plasma volume to several keV at densities of ≈ 3-6×1013cm−3.
Generation and confinement of hot ions and electrons in a reversed-field pinch plasma